A Light-Emitting Diode (LED), as used herein, is a semiconductor light source for generating a light at a specified wavelength or a range of wavelengths. LEDs are traditionally used for indicator lamps, and are increasingly used for displays. An LED emits light when a voltage is applied across a p-n junction formed by oppositely doped semiconductor compound layers. Different wavelengths of light can be generated by varying the bandgaps of the semiconductor layers (accomplished by, e.g., using different materials) and by fabricating an active layer (explained further below in the specification) within the p-n junction. Additionally, an optional phosphor material changes the properties of light generated by the LED.
Traditionally, LEDs are made by growing a plurality of light-emitting structures on a growth substrate. The light-emitting structures along with the underlying growth substrate are separated into individual LED dies. At some point before or after the separation, electrodes or metal pads are added to each of the LED dies to allow the conduction of electricity across the structure. LED dies are then packaged by adding a package substrate, bonding wires, a reflector, phosphor material, and/or lens to become an optical emitter.
Continued development in LEDs has resulted in light sources that can cover the visible spectrum and beyond. These attributes, coupled with the potentially long service life of solid state devices, may enable a variety of new display applications, and may place LEDs in a position to compete with the well entrenched incandescent and fluorescent lamps.
However, improvements in manufacturing processes to make highly efficient and mechanically robust LEDs continue to be sought.